Ignition system



Aug. 10, 1965 LE ROY E. DILGER IGNITION SYSTEM 2 Sheets-Sheet 1 FiledJan. 23. 1961 INVENTOR. LeRoy E.Di| ger M Attorney Aug. 10, 1965 LE ROYE. DILGER 3,200,291

IGNITION SYSTEM Filed Jan. 23. 1961 2 Sheets-Sheet 2 IN VEN TOR. LeRoyE. Dilger a/WM-L/ Attorney Breaker Closes FIG.4

United States Patent Office 3,20%,291 Patented Aug. 10, 1965 3,2tlti,29lIGNTTEQN SYSTEM Le Roy E. Diiger, Milwaukee, Wis, assignor to Globe-Union inc, Milwaukee, Wis, a corporation of Delaware Filed Jan. 23,1961, Ser. No. 84,292 29 Claims. (Si. 315-2tl5) This invention relatesto transistorized ignition systems for internal combustion engines.

Battery operated ignition systems used with internal combustion enginesstore the energy for ignition in the magnetic field of an ignition coil.This energy is proportional to the product of the amperes of currentflowing through and the number of turns of wire in the coil. With theupper limit of current fixed at about six amperes, it becomes necessaryto have considerable inductance (a large number of turns) in the coil inorder to store sulficient energy for ignition. The time that it takesfor the current in the coil to reach full value is proportional to theinductance of the coil. Thus, it can be seen that the more turns thereare in the coil, the longer the time it will take for the primarycurrent to reach full value. At high speed, with multi-cylinder engines,the primary coil current reaches only a fraction of its full value andavailable ignition power is reduced proportionately.

Considerable power is also wasted at low engine speed because theprimary current must be maintained at full level ready for the time ofignition. With the times for ignition widely spaced, as they are at lowengine speed, much power is wasted in the form of heat which causesbluing of the breaker contacts and deterioration of the coil insulation.Breaker contact life is further shortened because the contacts mustbreak a current of 4 to 6 amperes flowing in the high-inductance primaryof the ignition coil. The are caused by the rapid decay of current inthe ignition coil results in severe erosion of the breaker contacts anddeterioration of ignition performance.

The primary object of the present invention is to provide an ignitionsystem in which the full value of the ignition power is available athigh engine speeds and not wasted at low engine speeds.

Another object of this invention is to provide an ignition system inwhich the circuit breaker will have lessened erosion and longer life.

A further object is to increase the thermal content of the spark acrossthe spark gap.

Another object is to provide an ignition system which has highinstantaneous currents in the ignition coil primary.

Still another object is to provide an ignition system having moreprecise switching at high engine speeds and greater operating life. i

A still further object is to provide a more efficient ignition system bydrawing heavy current only during the actual ignition pulse.

Still another object is to provide an ignition system with substantiallyconstant energy for each spark throughout the entire engine speed range.

A final object is to increase the energy at the plugs when starting theengine.

These objects are accomplished by the circuitry of this invention. A lowinductance step-up transformer, that is, one having a small number ofturns in its primary and its secondary, increases the voltage to a levelsuitable for ignition by means of the well known principles ofinduction. A transistor is used to control the current through theprimary of the step-up transformer with a differentiating circuitconnected to the base of the transistor to decrease current flowexponentially from a maximum to a minimum. Due to the low inductance ofthe primary coil and the high momentary current flow from thetransistor, a voltage will be induced immediately in the secondary coilat a sufiiciently high level to produce :a spark suitable for properignition. For starting, a shunt circuit is used to bypass thedifferentiating circuit and cause the transistor to deliver more poweruntil the engine starts, thus providing a more intense spark to startthe engine.

Other objects and advantages will be pointed out in, or be apparentfrom, the specification and claims, as will obvious modifications of theembodiments shown in the drawings, in which:

FIG. 1 is a circuit diagram of an ignition system which will fire whenthe circuit breaker is closed;

FIG. 2 is a circuit diagram of a modified ignition system that fireswhen the circuit breaker is opened;

FIG. 3 is a variation of FIG. 1 arranged for firing when the circuitbreaker opens and the positive side of the battery is grounded;

FIG. 4 is a drawing of the Waveform which appears across X, Y in FIG. 1;and

FIG. 5 is a circuit diagram of a modified ignition system which includesa shunt circuit for starting.

The ignition systems shown in the drawings each include a low inductancetype step-up transformer 10 having a primary winding v12 and a secondarywinding 14 connected to .a distributor 16 which routes the current pulseinduced in the secondary winding to sparking devices iii. Because of therelatively small number of turns in the primary winding, the inductanceof the transformer is low and current flow through the primary windingwill reach a maximum almost instantly inducing a voltage in thesecondary winding which will initially charge capacitor 29 until thevoltage is sufiicient to bridge the natural gap in the distributor, atwhich time the capacitor will discharge across the sparking devices.This build up of vo-lt age in the capacitor increases the thermalcontent of the spark by consolidating the energy available and giving itup in an extremely short time. The instantaneous power dissipated in thespark is much greater than that normally dissipated in conventionalsystems.

The primary winding 12 of the transformer is connected to the negativeterminal of battery 22 and to collector 24 of transistor 26. Emitter 28is connected to the positive terminal of the battery. The base 36 of thetransistor is connected to a differentiating circuit which includes afirst resistor 32, a capacitor 34 and a circuit breaker 36 seriallyconnected across the battery. A second resistor 38 is connected inparallel with resistor 32. and capacitor 34. Considering the opera-tionof the differentiating circuit only with reference to the voltagewaveform (FIG. 4) between point X and point Y, it can be seen that withthe circuit breaker open, the circuit is quiescent. At the preciseinstant that the circuit breaker is closed, the entire voltage drop willappear across resistor 32 due to the charging of capacitor 34. Point Xwill be negative with respect to point Y. The capacitor will accumulatea charge at an exponential rate and the voltage across resistor 32. willdrop at an exponential rate until the total supply voltage appearsacross capacitor 34. When the circuit breaker is opened, the capacitorwill discharge through resistor 38 and resistor 32 in series. Thevoltage across resistor 32 will rise instantly to a value determined bythe ratio of the two resistances. The voltage at point X will then bepositive with respect to point Y. The capacitor will discharge at anexponential rate and the voltage across resistor 32 will drop to zero atan exponential rate.

Referring now to FIG. 1, it can be seen that resistance 32 forms theinput circuit for transistor 26 with point X at base 30 and point Y atemitter 28. Transistor 26 operates at cut-off (no collector currentflowing) by virtue of having the base connected to the positive side ofthe battery through resistor 32. The sharp negative swing of voltage atpoint X, when circuit breaker 36 closes,

azoaaor makes the base of the transistor negative with respect to theemitter and the transistor conducts heavily with its collector currentpassing through the primary of the transformer. Typical values ofcollector current are from 30 to 50 amperes compared to a maximum of sixarnperes in conventional systems. The sudden current passing through thetransformer primary winding causes a voltage to be induced immediatelyacross the secondary winding due to the low inductance of thetransformer. The voltage from the secondary winding charges capacitor 20until the voltage in the seocndary circuit reaches a value sufiicient tobridge the normal gap of the distributor and then discharges across thespark plug. The distributor, operating in synchronism with the circuitbreaker and the engine, will route the voltage to the proper spark plug.This arrangement makes it possible to enhance the thermal content of thespark by consolidating the energy available at the seocndary winding andgiving it up in an extremely short time. The instantaneous powerdissipated in the spark is much greater than that dissipated inconventional systems.

After the initial sharp turn-on pulse, the voltage applied to the baseof the transistor will decay at an exponential rate (FIG. 4) and quicklyreturns the transistor to the cut-oif condition. Thus it can be seenthat the transistor carries current for only a very brief instant andthere is no unnecessary dissipation. The positive pulse occuring whenthe breaker 36 opens only drives the transistor further into thecut-ofi? region. An ammeter 52 inserted in the position shown or asindicated in dotted lines will indicate increasing current withincreasing speed and can be calibrated in terms of speed so that it mayfunction as a tachometer.

Where a system is required which will fire the circuit breaker opens(FIG. 2), a phase inversion amplifier is inserted between capacitor 34and resistor 32 in order to use the positive pulse of thedifferentiating circuit for firing. The amplifier includes a secondtransistor 56 and a resistor 58 as shown in FIG. 2. The base 69 of thetransistor is connected to the negative terminal of battery 22 throughresistor 56 in order to bias the transistor to its full conduction. Thecollector 62 of the transistor is connected through resistor 32 to thebattery to cause a voltage drop across resistor 32 that is very nearlyequal to the supply voltage. This voltage drop has a positive polarityat the collector end of resistance 32 which is connected directly to thebase of transistor 26 and holds transistor 26 at collector currentcut-01f.

Capacitor 34 is charged by the battery when the circuit breaker isopened. When the circuit breaker is closed, the capacitor will dischargethrough resistance 58. This increases momentarily the negative polarityof the base of transistor 56. Since transistor 56 is fully conducting asthe result of the fixed negative bias, it cannot be made more conductiveby the negative pulse resulting from the closure of breaker 4. As aresult there is no net change in the rest of the circuit.

At the precise instant that the circuit breaker opens, capacitor 34 willstart to charge. The charging current is drawn through resistor 58 andresistor 38. At that precise instant of opening, a positive voltage of avalue determined by the resistance of resistors 38 and S and also thebase circuit resistance of transistor 56, appears at the base oftransistor 56. This positive pulse momentarily drives transistor 56 intocollector current cutoff. The collector of transistor 56 and the base oftransistor 26 will be brought toward the potential of the negativesupply terminal. The negative potential at the base of transistor 26drives it into full conduction and the remainder of the circuitfunctions as in FIG. 1. As the capacitor continues to charge, thepositive voltage across resistor 58 decays to zero and the circuitreturns to its initial quiescent condition. An ammeter 59 can also beconnected to this circuit to act as a tachometer as described above.

.as to drive transistor 26 into full conduction.

The circuit shown in FIG. 3 is for use with electrical systems havingthe positive battery terminal grounded to the chassis of the engine andis designed to fire when the circuit breaker opens. The circuit issimilar to the circuit described in FIG. 1 except that transistor 64 isused as the circuit breaker and circuit breaker 36 is used to controlthe conductivity of the transistor 64. When circuit breaker 36 isclosed, transistor 64 is biased to cut-off. Its base is returneddirectly to the positive battery terminal through the circuit breaker.Transistor 26 is at cut-oil. with its base returned to the positivebattery terminal through resistor 32. Capacitor 34 has no charge becausethe emitter of transistor 64 is also connected to the battery positiveterminal through resistor 32.

At the precise instant that the circuit breaker opens, transistor 64goes into full conduction because its base circuit is now returned tothe negative terminal of the battery through resistor 70. Capacitor 34charges through the transistor 64 and resistor 32. The charging currentcauses a negative voltage to a appear at point X which drives transistor24 into full conduction. As the charge on the capacitor approaches fullcharge, the voltage drop across resistor 32 falls to zero and the actionof the remainder of the circuit is the same as that described above.Closing the circuit breaker shifts transistor 64 back to the cut-offcondition. Capacitor 34 discharges through resistor 38 and resistor 32creating a positive pulse at point X" which only drives transistor 24further into collector current shut-off.

The circuit shown in FIG. 5 is for use in ignition systems having thenegative battery terminal grounded and is designed to fire when thecircuit breaker opens. The transformer secondary winding 14 functions asabove with the current induced in the secondary Winding chargingcapacitor 20 until the voltage in the secondary circuit is sufficient tobridge the normal gap of distributor 16 cansing a spark across thesparking devices 18.

Transistor 72 is used as a switch to control the charging of capacitor34. With circuit breaker 36 closed, transistor 72 is biased to fullconduction by virtue of the voltage appearing at the junction ofresistors 74 and 76 serially connected across battery 22. Theseresistors from a voltage divider across the battery when the circuitbreaker is closed and the voltage at their junction is selected to causefull conduction of the transistor. At full conduction there is verylittle voltage drop across transistor 72, therefore, the left side ofcapacitor 34 is, in effect, connected to the positive battery terminal.The right side of the capacitor is also returned to the positiveterminal of the battery. Since both sides of the capacitor are returnedto the positive side of the battery, the capacitor has no charge.

At the instant circuit breaker 36 opens, transistor 72 is biased tocut-off because its base is now returned to the positive batteryterminal through resistor 74. With transistor 72 at cut-off, capacitor34 is now efiectively in series with resistors 38 and 32 across battery22. The capacitor draws a heavy charging current that is at a maximumwhen the contacts open and decays to zero before they close again. Thecharging current across resistor 32 causes a voltage drop acrossresistor 32 of such polarity When the voltage again falls low enoughduring the exponential decay, transistor 26 will return to collectorcurrent cut-off. The abrupt turn-on of transistor 26 causes full currentflow through primary Winding 12 which induces the ignition voltage inthe secondary winding.

When the circuit breaker again closes, capacitor 34 discharges throughtransistor 72 collector-emitter circuit and resistor 32. The dischargeof capacitor 34 causes a voltage drop across resistor 32 of a polarityat the base of transistor 26 to drive it to collector current cut-off.

Because of the drain on the battery while driving the starting motor,the energy at the plugs will be at a minimum during starting. Toincrease the energy available during starting, resistor 80 and solenoidswitch 82 are serially connected across capacitor 34. Coil 84 of thesolenoid switch is connected to the coil terminal of the starter relayto close the switch when the starter relay is energized. This biasestransistor 26 into conduction during the entire period that the circuitbreaker 36 is open for each firing interval. This permits more energy tobe delivered to the plugs than would be the case if during such periodthe transistor cut-ofif the flow exponentially as in normal operation.De-energizing of the starter relay allows switch 82 to open and thecircuit operates normally.

Although but a few embodiments of the present invention have beenillustrated and described, it will be apparent to those skilled in theart that various changes and modifications may be made therein withoutdeparting from the spirit of the invention or from the scope of theappended claims.

I claim:

1. An ignition system for an internal combustion engine having a numberof spark plugs comprising, a low inductance transformer having a primarywinding and a secondary winding, a unidirectional voltage power supply,a transistor having its emitter connected to the positive terminal ofthe power supply and its collector to one end of the primary winding,the other end of the primary winding being connected to the negativeterminal of the power supply, differentiating circuit means connectedacross the power supply and without any impedance component interposeddirectly to the base of the transistor to provide an initially high biascurrent to the base of the transistor which decreases exponentially, andvoltage distribution means connected to the secondary winding todistribute the voltage induced in the secondary winding by the currentflow in the primary winding to the spark plugs.

2. An ignition system according to claim 1 wherein said differentiatingcircuit means includes circuit breaker means so that the transistor isconductive only when the circuit breaker is closed.

3. An ignition system according to claim 2 including phase inversioncircuit means connected between the differentiating circuit means andthe base of the transistor so that the transistor is conductive when thecircuit breaker is opened.

4. An ignition system according to claim 3 including a second transistormeans controlled by the circuit breaker so that the first transistor iscontrolled by the second transistor.

5. An ignition system for an internal combustion engine having a numberof spark plugs comprising, a low inductance transformer having a primarywinding and a secondary winding, a unidirectional voltage power supply,a transistor having its emitter connected to the positive terminal ofthe power supply and its collector to one end of the primary winding,the other end of the primary winding being connected to the negativeterminal of the power supply, circuit means including a capacitorconnected across the power supply and without any impedance componentinterposed directly to the base of the transistor to provide aninitially high bias current to the base of the transistor whichdecreases exponentially, said circuit means including a circuit breakerto control the charging of the capacitor, said transistor beingconductive only when the capacitor is charging, and voltage distributionmeans connected to the secondary winding to distribute the voltageinduced in the secondary winding by the current flowing from the primarywinding to the spark plugs.

6. An ignition system according to claim 5 wherein said circuit meansincludes a first resistance member connected in series with thecapacitor and a second resistance member connected in parallel with thefirst resistance member and the capacitor.

'7. An ignition system according to claim 6 wherein the breaker meansand distribution means are timed so that when the distribution means ispositioned to energize a spark plug the breaker means will be closed.

8. An ignition system according to claim 7 including an ammeterconnected between the negative terminal of the power supply and theprimary winding to indicate the engine speed in relation to current risethrough the windmg.

9. An ignition system for an internal combustion engine having a numberof spark plugs comprising, a transformer having a primary winding and asecondary winding, a unidirectional voltage power supply, a firsttransistor having its emitter connected to the positive terminal of thepower supply and its collector to one end of the primary winding, theother end of the primary winding being connected to the negativeterminal of the battery, differentiating circuit means including acircuit breaker connected across the power supply, a phase inversionamplifier connected across the power supply including a secondtransistor having its base connected to the diiferentiat ing circuit andits collector connected to the base of the first transistor, said secondtransistor being operative when the circuit breaker is closed to drivethe first transistor to collector current cut-01f, said differentiatingcircuit driving the second transistor momentarily to collect currentcut-oil when the circuit breaker is opened, allowing the firsttransistor to momentarily operate at full conductance, and voltagedistribution means connected to the secondary winding to distribute thevoltage induced in the secondary winding by the current flow in theprimary winding to the spark plugs.

10. An ignition system according to claim 9 wherein the circuit breakerand distribution means are timed so that circuit breaker is open onlywhen the distribution means is positioned to energize a spark plug.

11. An ignition system for an internal combustion engine having a numberof spark plugs comprising, a low inductance transformer having a primarywinding of a few turns and a secondary winding, a unidirectional voltagepower supply, a first transistor having its emitter connected to thepositive terminal of the power supply and its collector to one end ofthe primary winding, the other end of the winding being connected to thenegative terminal of the power supply, difierentiating circuit meansincluding a first and second resistor and a capacitor connected acrossthe power supply and to the base of the transistor, a transistorizedcircuit means connected in series with the differentiating circuit and acircuit breaker connected to control the energization of thetransistorized circuit means whereby the first transistor is conductiveonly when the transistorized circuit means is conductive, and voltagedistribution means including a capacitor connected across the secondarywinding to energize one of the spark plugs when the secondary voltagereaches a predetermined level.

12. An ignition system according to claim 11 wherein the circuit breakerand distribution means are timed so that circuit breaker is opened onlywhen the distribution means is positioned to energize a spark plug.

13. An ignition system for an internal combustion engine having a numberof spark plugs comprising, a low inductance transformer having a primarywinding and a secondary winding, a unidirectional voltage power supply,a first transistor having its emitter connected to the positive terminalof the power supply and its collector to one end of the primary winding,the other end of the winding being connected to the negative terminal ofthe power supply, diiferentiating circuit means including a resistanceand a capacitance connected across the power supply and without anyimpedance component interposed directly to the base of the transistor,circuit breaker means for controlling energization of thedifferentiating circuit to momentarily drive the transistor to fullconductance when the circuit breaker is open, and voltage distributionmeans connected across the secondary winding to energize one of thespark plugs when the secondary voltage reaches a predetermined level.

14. An ignition system according to claim 13 wherein said circuitbreaker means includes a second transistor connected to control thediflerentiating circuit whereby said differentiating circuit isoperative to drive the first transistor momentarily to full conductancewhen the second transistor is non-conductive.

15. An ignition system according to claim 14 including a shunt circuithaving a solenoid switch connecting the second transistor to the firsttransistor whereby said first transistor is fully conductive during theperiods when the circuit breaker is open and the solenoid switch isclosed.

16. An ignition system for an internal combustion engine having a sparkplug comprising, a low inductance transformer having a primary windingand a secondary winding connected to the spark ping, a unidirectionalvoltage power supply, a transistor having its emitter connected to thepositive terminal of the power supply and its collector connected to oneend of the primary winding, the other end of the primary winding beingconnected to the negative terminal of the power supply, impedancecircuit means connected across the power supply and Without anyimpedance component interposed directly to the base of the transistor tocontrol current conduction through the transistor, circuit breaker meansconnected to the circuit impedance means so that the impedance meansallows an initially high current to flow through the transistor, saidcurrent decreasing exponentially to a low value, and a capacitive meansconnected across the secondary Winding to enhance the thermal content ofthe spark by discharging across the spark plug when the voltage in thesecondary reaches a predetermined level.

17. An ignition system according to claim 16 wherein said impedancecircuit includes a first resistance and a capacitance serially connectedto the circuit breaker means with the base of the transistor beingconnected to the junction of the resistance and capacitance and a secondresistance connection in parallel with the serially connected firstresistance and capacitance.

18. An ignition system according to claim 17 wherein the circuit breakermeans includes a second transistor hav- 40 ing its emitter connected tothe junction of the second resistor and the capacitor and its collectorto the negative terminal of the power source, said first transistorbeing conductive when the second transistor is non-conductive.

19. An ignition system according to claim 16 wherein said impedancecircuit includes a first resistance, at capacitance and a secondresistance serially connected across the battery with the base of thefirst transistor connected to the junction of the capacitor with thefirst resistor, said circuit breaker means including a second transistorhaving its emitter connected to the positive terminal of the battery andits collector to the junction of the capacitor with the second resistor,and a voltage divider circuit connected across the power supply end tothe base of the second transistor whereby current flowing across thevoltage divider will cause the second transistor to conduct, causing theimpedance circuit to bias the first transistor to conduct current fullymomentarily.

20. An ignition system according to claim 19 including a shunt circuitfor the capacitor to allow the first transistor to conduct fully duringthe entire time that the second transistor is not conducting.

References Cited by the Examiner UNITED STATES PATENTS 2,685,050 7/54Smits 315-222 2,849,626 8/58 Klapp. 2,878,298 3 5 9 Giacolletto 3152092,904,723 9/59 Altrogge et al. 315-219 X 2,966,615 12/60 Meyer.3,083,306 3/63 Lindstrom et al. 3,088,079 4/63 Quigley. 3,089,964 5/63Bruce.

FOREIGN PATENTS 534,888 12/56 Canada.

1,211,857 10/59 France.

GEORGE N. WESTBY, Primary Examiner.

RALPH G. NILSON, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. August10, 1965 Le Roy E. Dilger It is hereby certified that error appears inthe above numbered patent requiring correction and that the said LettersPatent should read as corrected below.

Column 7, line 37, for "connection" read connected Signed and sealedthis 1st day of February 1966.

(SEAL) Attept:

ERNEST W. SWIDER Attesting Officer Commissioner of Patents EDWARD J.BRENNER

1. AN IGNITION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE HAVING A NUMBEROF SPARK PLUGS COMPRISING, A LOW INDUCTANCE TRANSFORMER HAVING A PRIMARYWINDING AND A SECONDARY WINDING, A UNIDIRECTIONAL VOLTAGE POWER SUPPLY,A TRANSISTOR HAVING ITS EMITTER CONNECTED TO THE POSITIVE TERMINAL OFTHE POWER SUPPLY AND ITS COLLECTOR TO ONE END OF THE PRIMARY WINDING,THE OTHER END OF THE PRIMARY WINDING BEING CONNECTED TO THE BEGATIVETERMINAL OF THE POWER SUPPLY, DIFFERENTIATING CIRCUIT MEANS CONNECTEDACROSS THE POWER SUPPLY AND WITHOUT ANY INPEDANCE COMPONENT INTERPOSEDDIRECTLY TO THE BASE OF THE TRANSISTOR TO